Study population
The characteristics of patients are presented in the Table 1. According to the age, primary disease, the presence of VF, VT, atrial fibrillation (AF), a history of MI, electrocardiography, echocardiography, MPS results, comorbidity and therapy of primary disease, there were no significant differences between groups (Table 1).
Table 1
Baseline characteristics of enrolled patients
|
1st group
(n = 40)
|
2nd group
(n = 29)
|
p
|
Sex, male/female (n, %)
|
38/2 (95.0/5.0 %)
|
27/2 (93.1/6.9 %)
|
0.898
|
Age (M ± SD, year)
|
64.2 ± 7.4
|
66.8 ± 7.9
|
0.352
|
Prior myocardial infarction older 3 month (n, %)
|
40 (100.0 %)
|
29 (100.0 %)
|
0.995
|
Myocardial infarction localization:
|
|
|
|
apical (n, %)
|
25 (62.5 %)
|
13 (44.9 %)
|
0.214
|
septal (n, %)
|
7 (17.5 %)
|
16 (55.2 %)
|
0.008
|
anterior (n, %)
|
5 (12.5 %)
|
21 (72.4 %)
|
0.001
|
posterolateral (n, %)
|
10 (25.0 %)
|
4 (13.8 %)
|
0.432
|
Hypertension I-III deg. (n, %)
|
18 (45.0 %)
|
15 (51.7 %)
|
0.639
|
NYHA functional class:
|
|
|
|
I (n, %)
|
0 (0.0 %)
|
3 (10.3 %)
|
0.469
|
II (n, %)
|
24 (60.0 %)
|
16 (55.2 %)
|
0.738
|
III (n, %)
|
16 (40.0 %)
|
10 (34.5 %)
|
0.701
|
QRS (Me [Q1-Q3], ms)
|
110.0 [100.0; 120.0]
|
100 [80; 120]
|
0.068
|
QTc (Me [Q1-Q3], ms)
|
420.0 [410.0; 453.5]
|
420.0 [397.0; 444.0]
|
0.567
|
LVEF (Me [Q1-Q3], %)
|
35.5 [31.0; 44.0]
|
42.0 [35.0; 55.0]
|
0.052
|
Summed rest score (Me [Q1-Q3], %)
|
20.0 [13.0; 30.0]
|
24.0 [8.0; 31.0]
|
0.927
|
Ventricle fibrillation (n, %)
|
0 (0.0 %)
|
1 (3.4 %)
|
0.812
|
Nonsustained ventricular tachycardia (n, %)
|
38 (95.0 %)
|
28 (96.5 %)
|
0.917
|
Sustained ventricular tachycardia (n, %)
|
18 (45.0 %)
|
21 (72.4 %)
|
0.054
|
Atrial fibrillation (n, %)
|
19 (47.5 %)
|
8 (27.6 %)
|
0.162
|
Dyslipidemia (n, %)
|
23 (57.5 %)
|
15 (51.7 %)
|
0.563
|
Diabetes mellitus (n, %)
|
4 (10.0%)
|
3 (10.3 %)
|
0.985
|
Obesity (n, %)
|
14 (35.0 %)
|
11 (37.9 %)
|
0.841
|
Therapy:
|
|
|
|
beta-blockers (n, %)
|
40 (100.0 %)
|
29 (100.0 %)
|
0.995
|
amiodarone (n, %)
|
16 (40.0 %)
|
15 (51.7 %)
|
0.411
|
statins (n, %)
|
40 (100.0 %)
|
29 (100.0 %)
|
0.995
|
Angiotensin-converting enzyme inhibitors (n, %)
|
38 (95.0 %)
|
26 (89.6 %)
|
0.710
|
Antiplatelet agents (n, %)
|
40 (100.0 %)
|
29 (100.0 %)
|
0.995
|
Diuretic (n, %)
|
28 (70.0 %)
|
18 (62.0 %)
|
0.580
|
Notes: M ± SD – mean ± standard deviation, NYHA – New York Heart Association, Me [Q1; Q3] – median [lower-upper quartile], LVEF – left ventricle ejection fraction. |
Clinical and ICD implantation data
According to the results of MPS with 99mTc-MIBI, all 69 (100.0 %) patients showed perfusion defects indicating a myocardial scar, medium SRS was 20.0 % [13.0; 30.0]. An example of obtained scintigrams is presented in Fig. 4.
Results of myocardial perfusion scintigraphy with 99mTc-MIBI are presented in Table 2. In 32 (80.0 %) of patients from the 1st group, perfusion defects were more significant in the apical segment then in septal segments and DL was implanted to the septum of the right ventricle. The other 8 (20.0 %) patients have predominantly perfusion defects in the septal segment and DL was implanted to the zone of the smallest perfusion disorders (myocardial scar), that is apex of the right ventricle. In 10 (34.5 %) patients from the 2nd group, the predominantly perfusion defects indicating a myocardial scar in the apical segment was larger than in the septal segment. The other 19 (65.5 %) patients have predominantly perfusion defects in the septal segment. But in this group DL was implanted only according to the conventional approach, in 16 (55.2 %) patients DL was implanted to the septal position (p = 0.081), and in 13 (44.8 %) - apical (p = 0.081).
Table 2
Results of myocardial perfusion scintigraphy with 99mTc-MIBI
|
1st group
(n = 40)
|
2nd group
(n = 29)
|
p
|
Summed rest score, %
|
20.0 [13.0; 30.0]
|
24.0 [8.0; 31.0]
|
0.927
|
Summed apical score
|
4.0 [1.0; 7.0]
|
3.0 [0.0; 6.0]
|
0.212
|
Summed septal score
|
2.5 [1.0; 3.0]
|
5.0 [1.0; 7.0]
|
0.053
|
In the 1st group (n = 40) single-chamber ICD was implanted in 4 (10.0 %) patients, in the 2nd group (n = 29) – 3 (10.3 %) patients (p = 0.193), dual-chamber – 36 (90.0 %) vs. 26 (89.7 %) (p = 0.274). In the 1st group for 20 (50.0 %) patients ICD was implanted for primary SCD prevention, in the 2nd group – 8 (27.6 %) (p = 0.287), secondary prevention – 20 (50.0 %) vs. 21 (72.4 %) (p = 0.287). |
Examples of patients with DL in septal and apical positions are presented in Fig. 5.
ICD implantation was uneventful and there were no complications and death. There was no ICD-related surgical revision during 12 month after implantation. There were no leads dysfunction (except PT increase more 1.0 V and VSA decrease less 5.0 mV) and dislocation.
ICD interrogation data
The follow-up for 12 month was complete in 69 (100.0 %) patients. Significant differences between patients from both groups were found for PT and VSA at all control follow-up points (Table 3).
Table 3
Defibrillation lead indicators at control points Mₑ [Q₁; Q₃]
Indicator
|
1st group, n = 40
|
2nd group, n = 29
|
p
|
1st day after ICD implantation
|
PT, V
|
0.5 [0.4; 0.5]
|
0.7 [0.7; 1.1]
|
< 0.001
|
VSA, mV
|
12.5 [11.7; 12.5]
|
8.5 [7.0; 10.5]
|
< 0.001
|
PI, Ohm
|
526.0 [491.0; 572.0]
|
496.0 [445.0; 501.0]
|
< 0.001
|
SI, Ohm
|
54.0 [51.0; 65.0]
|
58.0 [54.0; 69.0]
|
0.171
|
1st month after ICD implantation
|
PT, V
|
0.5 [0.3; 0.65]
|
1.2 [0.9; 1.3]
|
< 0.001
|
VSA, mV
|
13.5 [12.0; 14.5]
|
6.0 [5.0; 6.5]
|
< 0.001
|
PI, Ohm
|
523.0 [484.5; 559.5]
|
605.0 [585.0; 634.0]
|
< 0.001
|
SI, Ohm
|
54.0 [50.5; 62.5]
|
57.0 [53.0; 60.0]
|
0.312
|
6th month after ICD implantation
|
PT, V
|
0.5 [0.3; 0.7]
|
1.1 [0.8; 1.2]
|
< 0.001
|
VSA, mV
|
13.7 [12.0; 14.5]
|
6.5 [5.5; 9.6]
|
< 0.001
|
PI, Ohm
|
496.0 [442.0; 553.0]
|
565.0 [475.0; 614.0]
|
0.012
|
SI, Ohm
|
55.0 [49.5; 64.0]
|
57.0 [52.0; 60.0]
|
0.626
|
12th month after ICD implantation
|
PT, V
|
0.5 [0.5; 0.65]
|
1.1 [0.9; 1.3]
|
< 0.001
|
VSA, mV
|
14.25 [12.0; 15.2]
|
6.8 [5.5; 10.0]
|
< 0.001
|
PI, Ohm
|
486.0 [417.0; 519.5]
|
475.0 [420.0; 574.0]
|
0.454
|
SI, Ohm
|
62.0 [46.0; 72.0]
|
55.0 [51.0; 62.0]
|
0.191
|
Notes: ICD – implanted cardioverter-defibrillator, PT – pacing threshold, PI – pace impedance, VSA – ventricle signal amplitude, SI – shock impedance. |
PT in the 1st group was lower than in the 2nd group at all control points (p < 0.001). The PT dynamics in groups at all follow-up points is shown in the Fig. 6.
VSA in the 1st group was higher than in the 2nd group at all follow-up points (p < 0.001). The VSA dynamics in groups at all follow-up points is shown in the Fig. 7.
It should be noted that in the 1st group in 2 (5.0%) patients was registered VSA less than 7.0 mV and in the 2nd group – 23 (79.3%) (p < 0.001).
Lead impedance in the 2nd group was significantly higher than in the 1st group on the 1st (p < 0.001) and 6th (p = 0.012) month control follow-up points (Table 3). Shock impedance did not significantly differ (Table 3). A critical increase or decrease of the pacing and shock impedance in both groups was not detected (normal pacing impedance 200–2000 Ohms, normal shock impedance 20–200 Ohms).
During 12th month follow-up an appropriate ICD-therapy was registered in 6 (8.7%) patients from both groups, 2 (2.9%) patients of them received ICD-shock, 4 (5.8%) – ATP-therapy. In the 1st group 4 of 40 patients (10.0%) received an appropriate ICD-therapy, in the 2nd group – 2 of 29 patients (6.9%) (p = 0.423), ICD-shock – 2 (5.0%) vs. 0 (0%) (p = 0.728), ATP-therapy – 2 (5.0%) vs. 2 (6.9%) (p = 0.845). In 1st group non-sustained VT was registered in 24 of 40 patients (60.0 %) with spontaneous termination, in 2nd group – 18 of 29 patients (62.1%) (p = 0.888).
In the 1st group an inappropriate ICD-therapy (ICD-shock/ATP-therapy) was not registered. An inappropriate ICD-therapy (ICD-shock/ATP-therapy) was registered in 3 (4.4 %) patients from the 2nd group (p = 0.584). These episodes were related with ventricular signal hyposensing, because all 3 patients had low VSA (less than 5.0 mV) and DL sensitivity was automatically lower. This led to T-wave oversensing on sinus tachycardia. ICD interpreted this event as VT and performed ICD-therapy.
In the 2nd group, comparison of the DL implantation site with the MPS results showed that in 11 (37.9%) patients DL was implanted in the segment with the maximum perfusion defects. Thus, DL implantation according to the conventional approach, when the myocardial scar is not assessed before the operation, could lead to an PT increase and VSA decrease. Among these 11 patients, 3 of them have inappropriate ICD-therapy. All three patients had dual-chamber ICDs with adequate settings for VT/VF detection. It is noteworthy that the amplitude of the VSA in these patients was less than 5.0 mV and it’s could be reason of inappropriate ICD-therapy.
In this way, DL implantation in the 1st group after the radionuclide assessment of myocardial perfusion (myocardial scar) in the apical and septal segments allowed to achieve optimal PT (p < 0.001) and VSA (p = 0.001) indicators.